Objective  To understand the relationship between water and carbon metabolism and growth and fruiting of branches at different positions in the crown of Hippophae rhamnoides for providing a certain theoretical basis for the formulation of cultivation technical measures for Hippophae rhamnoides tree shape culture.

Method  According to the two-year-old branches in the upper, middle and lower crown of Hippophae rhamnoides, water status, photosynthesis, non-structural carbohydrate (NSC) content, branch and leaf growth, fruiting traits and fruit nutrients were compared.

Result  The results showed that there was no significant difference in the pre-dawn water potential of branches in different parts of the crown, and the water potential of the bottom branches at midday was significantly higher than that of the upper and middle branches. The percentage loss of conductivity (PLC) of the middle branch in pre-dawn was significantly lower than that of upper and lower branches, and the PLC of the bottom branch at midday was significantly higher than that of top and middle branches. The stem and leaf area specific hydraulic conductivity of upper branches was significantly higher than that of middle and lower branches. The net photosynthetic rate in the top branch was the largest, followed by middle branch and bottom branch. NSC content in xylem of middle branches was significantly higher than that of upper branches, but there was no significant difference between the upper and lower branches, as well as between the middle and lower branches. There was no significant difference in NSC content in phloem among branches, and the NSC content in leaves of upper and middle branches was significantly higher than that of lower branches. The longitudinal and transverse diameter of flower buds, the proportion of pure flower buds, the germination rate, the number of new shoots, the basal diameter of new shoots, the leaf area and the specific leaf mass of the bottom branches were significantly lower than those of the upper and middle branches. The longitudinal and transverse diameter of fruit, fruit setting rate and soluble solid content of the bottom branches were both lower than those of the upper and middle branches. The branch length and base diameter of the upper branches are significantly higher than that of the middle branch. The fruit quality and fruit vertical and horizontal diameter of the middle branch were significantly higher than those of the upper branch. There was no significant difference in the contents of flavonoids, vitamin C and titratable acid among different branches.

Conclusion  The lower branches are greatly affected by shading, which significantly restricts the uptake and growth of photosynthetic products, and affects their fruiting traits. The upper branches are dominant in growth, and the middle branches are dominant in fruiting traits. Therefore, the tree-shaped cultivation of Hippophae rhamnoides should take full account of its light conditions, and timely remove the branches in the lower light area. At the same time, we should pay attention to the balance between nutritional growth and reproductive growth, and making full use of the upper and middle branches of the crownfor improving the yield and quality of Hippophae rhamnoides.